Plural beam electron gun



E. J. VAN BARNEVELD ETAL PLURAL BEAM ELEcTRoN GUN Filed June 2o, 1960 Feb. 11, 1964 United States Patent O 3,121,181 PLURAL BEAD/i ELECTRN GUN Evert Jau van Barneveld, Hendrikus Johannes Lemmens, Gerardus Arnoldus Herman Maria Vriissen, Hendrik Budgett, Johannes Hendrikus Theodorus van Roosmaien, and .lohannes van Esionis, ali of Eindhoven, Netherlands, assignors to North American Philips Company inc., i Tew York, NX., a corporation of Delaware Filed .lune 20, 196i), Ser. No. 37,498 Ciaims priority, application Netherlands duly 9, 1959 10 Claims. (Cl. 313-82) This invention relates rto electron guns Ilfor producing two electron rays which can be controlled in intensity independently of each other and which extend closely in parallel to each other. Such au electron gun may be used in a display tube for colour television pictures, which operates on the index principle and in which the rays eX- plore in common a 'viewing screen .consisting of colour lines in a direction at right angles to these colour lines. The term colour line is to be understood herein to mean a phosphorus line which luminesces in `a given colour when struck by electrons. One ray serves to luminesce given points of the colour lines, whereas the second ray, which conveys a weak current, serves to identify the current pulses produced in the screen by the other ray. The two rays extend in parallel and las closely as possible one above the other, the electron current of the second r-ay being too weak to bring about troublesome luminescence of the colour lines. l

Each control electrode in vthe gun may be formed as a conventional control electrode cut through in the direction ot its length and comprising a cylindrical sleeve having either a plate welded thereon, or a cap obtained by deep drawing. However, this construction gives rise to the problem of rigidly securing such semi-cylindrical electrodes, because it has usually been found that the control electrodes are liable to vary their mutual positions, for example, due to deformation resulting from thermal expansion.

It has new proved possible to avoid this problem and, in addition, to obtain `a very rigid structure by again combining the two separate control electrodes so as to form a unitary structure. According -to the invention, this is obtained in that the control electrodes for the two beams, each comprising an apertured metal plate, have their straight sides Iarranged closely opposite each other and the remaining portions of their peripheries secured to supporting members which are `anchored in an enveloping supporting cylinder with the interposition of insulating material. The insulating material may preferably consist wholly of glass, but if the control electrodes become very hot, it is possible to use la combination of ceramic material yand glass, the glass then being provided at the end which is least hot and serving .to secure the supporting members and the ceramic insulating member.

In order that the invention may be readily carried into effect, it will now be described in detail, by way of example, with reference Ito the accompanying diagrammatic drawing, in which:

FIGURE l is a `cross-sectional view ot -a given embodiment of an electron gun according to the invention;

FIGURES 2 and 4 are cross-sectional views of further embodiments of the control electrodes iaccording to the invention, land FIGURE 3 is a plan View of the embodiment of FIG- URE 2.

In FIGURE l, a cathode 1 is shown diagrammatically. Opposite the electron-emissive surface of the cathode 1 there lare arranged semi-circular control electrodes 5 and 6 provided with apertures 2 `and 3, respectively, which form electron rays 2 and 3.

ICC

The control electrodes 5 and 6 have their straight edges positioned opposite each other, resulting in a gap 4 being formed. The electrons 4' which pass through it are intercepted by an Ianode 11, while the rays 2 `and 3 cau pass through corresponding taper-hires of Athe anode 11.

The semi-circular control electrodes 5 and 6 have the portions of their peripheries which are not opposite each other, secured to semi-cylindrical supporting members 7 and 8 respectively, which are provided with supply conductors. The control voltages are adjusted so that, for example, ray 2', which has to produce the image, has an intensity much greater than that of ray 3. The Supporting members 7 and 8 are secured by means of a suitable glass 10 and a glass to metal seal in an enveloping cylinder 9 which serves as a supporting member for the control electrodes and, in the case under consideration, also for the anode 11. The glass layer 10 is preferably closed at its ends by means of ceramic rings 28. The glass is thus prevented from flowing away when the supporting members 7 and 8 are secured by melting to the cylinder 9, while at the same time the members 7 and 8 are maintained centered.

Since the cylinder 9 is insulated from the control electrodes 5, 6 and their supporting members 7, 8 by means of the glass layer 10, it has become possible for the anode 11 to be joined directly to the cylinder 9. For this purpose the anode 11 is provided with a cylindrical portion which exactly tits around the cylinder 9 or a portion thereof which has been machined. The spacing between the control electrodes 5, 6 and the anode 11 is adjusted by the interposition of a template, whereupon apertures are drilled in the anode l1 and in the cylinder 9. After removal of the template, the anode is once again slipped on the cylinder 9 until the apertures are exactly aligned. The anode is then secured to cylinder 9 by inserting pins 12 into the apertures.

To permit the paths of the rays 2 and 3 to be acted upon, an auxiliary electrode 14 is provided which is secured by means of glass seals lll to pins 13 provided on the anode 1i. A second anode 15, which is usually supplied with a very high voltage, is connected by means of supporting rods 16 and three glass rods 17, only one of which is shown, to the auxiliary electrode 14 and secured inside the tube. When use is made of a triode gun, in which event the second anode is omitted, the glass rods 17 may be dispensed with and the gun can be secured in the tube by means of rigid current supply conductors only, thus permitting the neck of the cathode-ray tube to be materially narrowed.

By means of this construction, it has been found that the supporting members 7 and 8 can be so securely mounted in the cylinder 9 that the upper edges of the members 7 and 8 can be machined to size prior to the control electrodes 5 and 6 being welded thereon.

It the gun becomes so hot that the glass 10 would melt, the cement employed may be a ceramic mass 18, as shown in FlG. 2, such yas (A1203), which, atteihaving been provided, is sintered in position. lIn order to obtain a better connection, it is possible to weld a plurality of rods i9 and 2G, respectively, to the inner surface of the cylinder 9 and to the outer surface of the members 7 and 8, as shown in FIGURES 2 and 3, so that the grip of the ceramic mass 1S on the cylindrical surfaces 7, 8 and 9 is improved.

In the embodiment shown in FIGURE 4, the control electrodes 5, 6 are secured to supporting members 21, 22 which, in turn, are mounted in the anged supporting cylinder 25. Members 21, 22 are provided with anges 23, 24 and are separated from cylinder 25 by means of a flanged ceramic member. The various parts are connected together and sealed at the outer edges of lthe flanges by means ot glass 27, which forms a glass to metal seal.

In one specific embodiment, the apertures 2 and 3 have a diameter of 300 microns and the gap between the molybdenum electrodes 5 and 6 has a width of, say, 100 microns. The distance between the centers of the apertures 2 and 3 is 750 microns and the cathode l has a diameter of 4 millimeters. The supporting cylinder 9 has an inner diameter of l0 millimeters and the glass layer l() has a thickness of about 750 microns. A suitable composition of the glass for melting together the molybdenum parts 7, S and 9 is, for example:

Percent by weight 39 Although a few embodiments have been described the invention is also applicable to electrodes of different shape. Thus, it is possible for the supporting members to have a height so small that they may be constituted by bent ends of the supply conductors. The capacitance between the control electrodes and with respect to the supporting cylinder 9 thus becomes much less.

In addition, it is not necessary for the electron gun to have a circular cross-section.

What is claimed is:

l. An electron gun assembly for producing two electron beams directed along a longitudinal axis and individually controllable in intensity, comprising iirst and second beam intensity control electrodes, said electrodes each comprising a planar portion arranged substantially perpendicular to said axis and a body portion extending from a peripheral portion of said planar portion in the direction of said longitudinal axis, the planar portions being arranged with respective edges in spaced confronting relationship and said body portions deiining in combination a single tubular extension of said planar portions, a tubular member surrounding said extending body portions, an electrically insulating material having good heat conducting properties interposed between said body portions and said tubular member, means for securing together said body portions and said tubular member, and an electron emitting cathode arranged within the space deiined by said body portions and in cooperative relationship with said planar portions.

2. An electron gun assembly for producing two electron beams directed along a longitudinal axis and individually controllable in intensity, comprising irst and second beam intensity control electrodes, said electrodes each comprising a planar circular segment portion arranged substantially perpendicular to said axis and a body portion extending from the periphery of said planar portion in the direction of said longitudinal axis, the planar portions being arranged with respective edges in spaced confrontng relationship and said body portions defining in combination a cylindrical extension of said planar portions, a cylindrical member surrounding said extending body portions, an electrically insulating material interposed between said body portions and said cylindrical member, means for securing together said body portions and said cylindrical member, and an electron emitting cathode arranged Within the space defined by said body portions and in cooperative relationship with said planar portions.

3. An electron gun assembly as claimed in claim 2 wherein said planar portions are semi-circular discs `and said body portions are half-cylinders.

4. An electron gun assembly for producing two electron beams directed along a longitudinal axis and individually controllable in intensity, comprising iirst and second beam intensity control electrodes, said electrodes each comprising a planar circular segment portion arranged substantially perpendicular to said axis and a body portion extending from the periphery of said planar portion in the direction of said longitudinal axis, the planar portions being arranged with respective edges in spaced confronting relationship and said body portions defining in combination a single cylindrical extension of said planar portions, a cylindrical member surrounding said extending body portions, a glass layer interposed between said body portions and said cylindrical member thereby to insulate the same relative to each other, and to secure said body portions to said tubular member, and an electron emitting cathode arranged within the space deiined by said body portions and in cooperative relationship with said planar portions.

5. An electron gun assembly for producing two electron beams directed along a longitudinal axis and indi-V vidually controllable in intensity, comprising iirst and second bearn intensity control electrodes, said electrodes each comprising a planar circular segment portion arranged substantially perpendicular to said axis, a body portion extending from the periphery of said planar portion in the direction of said longitudinal axis and aV flange portion extending from said body portion, said planar portions being arranged with respective edges in spaced confronting relationship and said body portions delining in combination a tubular extension of said planar portions, a tubular member provided with a ange and surrounding said extending body portions, an electrically insulating material interposed between said body portions `and said tubular member, means for securing together the anges of said body portions and of said tubular member, and an electron emitting cathode arranged within the space defined by said body portions and in cooperative relationship with said planar portions.

6. An electron gunV assembly for producing two electron beams directed along a longitudinal axis and individually controllable in intensity, comprising iirst and second beam intensity control electrodes, said electrodes each comprising a planar portion arranged substantially perpendicular to said axis and a body portion extending from the periphery of said planar portion in the direction of said longitudinal axis, the planar portions being arranged with respective edges in spaced confronting relationship and said body portions dening in cornbination a cylindrical extension of said planar portions, a tubular member surrounding said extending body portions, an electrically insulating material interposed between said body portions and said tubular member, means for securing together said body portions and said tubular member, an electron emitting cathode arranged within the space defined by said body portions and in coopera` tive relationship with said planar portions, and an anode having a planar portion spaced from the control electrodes and a cylindrically extending portion surrounding and secured to sm'd tubular member.

7. An electron gun assembly for producing two electron beams directed along a longitudinal axis and individually controllable in intensity, comprising rst and second beam intensity control electrodes, said electrodes each comprising a planar circular segment portion arranged substantially perpendicular to said axis and a body portion extending from the periphery of said planar portion in the direction of said longitudinal axis, the planar portions being arranged with respective edges in spaced confronting relationship and said body portions deiining in combination a cylindrical extension of said planar portions, a cylindrical member surrounding said extending body portions and spaced therefrom, rod shaped members secured to the outer surface of said body portions and the inner surface of said cylindrical member, a glass layer interposed between said body portions and said cylindrical member thereby to insulate the same relative to each other and to secure said body portions to said cylindrical member, and an electronV emitting cathde arranged within the space defined by said body portions and in cooperative relationship with said planar portions.

S. An electron gun assembly for producing two electron beams directed along a longitudinal axis and individually controllable in intensity, comprising rst and second beam intensity control electrodes, said electrodes each comprising a planar circular segment portion arranged substantially perpendicular to said axis and a body portion extending from the periphery of said planar portion in the direction of said longitudinal axis, the planar portions being arranged with respective edges in spaced confronting relationship and said body portions defining in combination a cylindrical extension of said planar` portions, a cylindrical member surrounding said extending body portions, a glass sleeve interposed between said body portions and said cylindrical member thereby to insulate the same relative to each other and to secure said body portions to said cylindrical member, ceramic insulating rings arranged between said body portions and said cylindrical member at the extremities of the glass sleeve, and an electron emitting cathode arranged within the space defined by said body portions and in cooperative relationship with said planar portions.

9. An electron gun assembly for producing two electron beams directed along a longitudinal axis and individually controllable in intensity, comprising iirst and second beam intensity control electrodes, said electrodes each comprising an apertured planar semi-circular disc portion arranged substantially perpendicular to said axis and a semi-cylindrical body portion extending from the curved portion of the periphery of said planar portion in the direction of said longitudinal axis, the planar portions of said discs being arranged with their respective straight edges in spaced confronting relationship and said body portions defining in combination a single cylindrical extension of said planar portions, a tubular member surrounding said extending body portions, an electrically insulating material interposed between said body portions and said tubular member, means for securing together said body portions and said tubular member, and an electron emitting cathode arranged within the space defined by said body portions and in cooperative relationship with the apertures in said planar portions.

10. Apparatus as described in claim 9 further cornprising a cylindrical anode surrounding and secured to said tubular member and having a planar portion at one end thereof spaced from said control electrodes, said anode further comprising at least two apertures each 0E which is individually aligned with the respective apertures in said control electrodes.

References Cited in the le of this patent UNITED STATES PATENTS 2,556,824 Schade June 12, 1951 2,712,087 Fite et al. June 28, 1955 2,852,716 LaiTerty Sept. 16, 1958 2,891.183 Barnett June 16, 1959 

1. AN ELECTRON GUN ASSEMBLY FOR PRODUCING TWO ELECTRON BEAMS DIRECTED ALONG A LONGITUDINAL AXIS AND INDIVIDUALLY CONTROLLABLE IN INTENSITY, COMPRISING FIRST AND SECOND BEAM INTENSITY CONTROL ELECTRODES, SAID ELECTRODES EACH COMPRISING A PLANAR PORTION ARRANGED SUBSTANTIALLY PERPENDICULAR TO SAID AXIS AND A BODY PORTION EXTENDING FROM A PERIPHERAL PORTION OF SAID PLANAR PORTION IN THE DIRECTION OF SAID LONGITUDINAL AXIS, THE PLANAR PORTIONS BEING ARRANGED WITH RESPECTIVE EDGES IN SPACED CONFRONTING RELATIONSHIP AND SAID BODY PORTIONS DEFINING INCOMBINATION A SINGLE TUBULAR EXTENSION OF SAID PLANAR PORTIONS, A TUBULAR MEMBER SURROUNDING SAID EXTENDING BODY PORTIONS, AN 